Question 1

What is a hartree?

Accepted Answer

Atomic unit of energy used in quantum chemistry. 1 Hartree = 4.3597 × 10⁻¹⁸ J = 27.211 eV.

Question 2

Where are hartrees used?

Accepted Answer

Computational chemistry, atomic physics, molecular orbital calculations. Named after Douglas Hartree.

Question 3

What's the difference between energy and power?

Accepted Answer

Energy (joules, kWh) is total work done. Power (watts) is energy per unit time. A 100W bulb for 10 hours = 1 kWh of energy.

Question 4

Why are there so many energy units?

Accepted Answer

Different fields developed their own: BTU for heating, calories for nutrition, joules for physics, kWh for electricity billing.

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